Leanest Teens are Biggest Energy Users, Consumers

Teens who are most physically active and consume the most calories are the leanest, researchers say.

“The takehome message is to encourage your child to do as much physical activity as possible, including at least one hour of moderate to vigorous physical activity daily,” said Dr. Paule Barbeau, an MCG exercise physiologist and corresponding author on the paper in the April issue of The International Journal of Obesity. “This allows your child to eat more calories, which encourages more healthy eating habits while remaining in energy balance.”

Unfortunately, even the leanest of the 661 healthy Augusta teens in the study lacked good eating habits, researchers noted.

In fact, researchers couldn’t compare the diet quality of leaner and chubbier teens because it was so poor overall, said Inger StallmannJorgensen, research dietitian and the paper’s first author.

“Most did not have enough wholegrain food, lowfat dairy products, fruits or vegetables,” Ms. StallmannJorgensen said. Dietary mainstays included starches, salty snacks and soft drinks.

“Eating habits formed during our youth tend to stay with us into adulthood, so this does not bode well for prevention of chronic diseases such as diabetes and heart disease,” Ms. StallmannJorgensen noted.

Researchers queried participants about their physical activity and diet over at least four 24hour periods and calculated body fat percentages. They performed magnetic resonance imaging exams on most participants to measure visceral adipose tissue.

“Eightto 12yearolds can have enough that it’s more highly correlated with cardiovascular risk factors than overall percent body fat,” said Dr. Barbeau, noting that even relatively thin children can have enough visceral fat to be a health problem.

Surprisingly, they found teens who ate the most tended to have the least visceral body fat, probably because of their higher activity levels. Conversely, some teens who ate the least had the highest percentage of body fat.

“We expected the energy intake to be lower in kids who were leaner, but we realized the leaner kids were at a different energy balance than the others,” Dr. Barbeau said.

On average, female study participants had 30 percent body fat (high for females) and males had a healthier 18 percent. Genetics also plays a role in the body fat equation, researchers noted.

About 36 percent of highschool students—mostly males—meet recommendations for daily physical activity, according to the Centers for Disease Control and Prevention. On school days, 21 percent of students play video games or use the computer recreationally three or more hours, and 37 percent watch three or more hours of television, a CDC survey showed.

In the MCG study, common teen activity included watching a movie or spending time with friends. The most physically active teens tended to be males who participated in organized sports or exercises they could do alone or with friends.